This invention relates to a process and apparatus for reading two slivers to a spinning unit which are each taken out of a sliver feed and which are drafted and spun in the spinning unit, after which the two yarn components are guided together to form a double yarn and, as a double yarn, are wound onto a package which is used as a feeding package for a subsequent twisting.
In the case of a process and an arrangement of the initially mentioned type (German Patent Document DE-A 38 00 810), it is known to monitor the presence of the two entering slivers which are withdrawn from spinning cans or from sliver wind-up machines. Even if only one sliver is absent, the spinning operation is interrupted.
It is an object of the invention to provide a process of the initially mentioned type by means of which, when one or both of the slivers run out, a piecing of new slivers is carried out in such a manner that as little fiber material as possible will be lost.
According to a first solution proposed by the present invention, it is provided that, when one or both slivers run out, the possibly still existing sliver is cut off, new sliver feeds are applied to the spinning unit, and the two sliver ends are each connected with the starting portion of a new sliver at points which are offset with respect to one another in the travelling direction.
This first solution is based on the fact that in many cases, because of the formation of the connecting points that is offset in the travelling direction, no impermissible thick points are formed in the yarn so that the spinning operation can be continued virtually without any loss of fiber material after the running-out of one or of both slivers.
In this solution, it is provided in an advantageous further development of certain preferred embodiments of the invention that the double yarn is monitored with respect to thick points. When an excessive thick point occurs, the spinning operation is interrupted, after which a piecing is carried out during which the thick point is removed from the double yarn travelling onto the spool package. This measure is particularly advantageous when a double yarn is spun from very fine yarn components on which high demands are made with respect to quality as far as uniformity is concerned.
According to a second solution proposed by the present invention, it is provided that, when one or both slivers run out, the possibly still existing sliver is cut off, new sliver feeds are applied to the spinning units, the two sliver ends are connected at connecting points situated side-by-side with the starting portion of a respective new sliver, and the sections of the yarn components containing the connecting points are subsequently separated from the production of the double yarn.
In this solution, it is basically provided that the connecting points between the old incoming slivers and the new slivers do not enter into the double yarn which remains on the spool and is to be processed later. However, in this case, the amount of fiber material that must be removed, is limited to a minimum.
In a further development of certain preferred embodiments of this solution of the invention, it is provided that, when one or both of the slivers run out, the spinning operation is interrupted and that, after the connecting of the sliver ends with the starting portion of one new sliver respectively, a piecing is carried out during which, before or during the piecing according to certain preferred embodiments of the invention, the sections of the yarn components are removed which contain the connecting points. When the sections containing the connecting points are removed before the piecing according to other preferred embodiments of the invention, this may be carried out by the control of the spinning unit which carries out a corresponding method of operation as a result of the signals indicating the absence of the slivers. If the removal takes place during the piecing, this can be carried out by a servicing arrangement which carries out the piecing. In this case, the servicing arrangement receives a corresponding signal from the control of the spinning unit which causes the servicing device to carry out a special piecing program which is designed for the removal of the sections of the yarn components containing the connecting points.
In a further development of preferred embodiments of the second solution, it is provided that the spinning operation is interrupted after the connecting of the ends of the slivers with the starting portion of a respective new sliver and after the section of the double yarn containing the connecting points has moved onto the spool package, and that subsequently a piecing operation is carried out in which the section of the double yarn is removed which contains the connecting points. In the case of this process, it may be provided that the piecing of the new slivers is carried out without the interruption of the spinning operation. However, it is also contemplated in certain embodiments to interrupt the spinning operating for the piecing of the new slivers, then carry out a piecing operation, and then interrupt the spinning operation again and subsequently carry out the piecing operation with the removal of the section of the double yarn which contains the connecting points. In this case, the fiber quantity which corresponds to the connecting points does not have to be removed by devices that are part of the machine. On the contrary, this may be carried out by a servicing device which carries out the piecing operation and which is equipped with a collecting container for the fiber quantity to be removed which can be emptied.
In a further development of preferred embodiments of the invention, it is provided that, for carrying out the process, the spinning unit is equipped on its inlet side with devices for detecting the presence or absence of the slivers which are assigned to both slivers, with devices for cutting the slivers and with at least one part of devices for connecting the ends of the two incoming slivers, in each case, with a starting portion of a new sliver.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.